XML Basics

XML is a language used to create Web applications. It allows Web application designers to create their own customized tags, enabling the definition, transmission, validation, and interpretation of data between applications.

Some of the benefits of XML are:

• Information sharing. Any data can be stored in the XML format and be used by various tools that read data, write data, and transform data between XML and other formats. This is possible because of the separation of data and presentation.

• Content delivery. XML supports different users and channels, such as digital TV, Web, and multimedia. This helps in delivering e-business applications to customers through their chosen media.

• Extensibility. As the name suggests, XML supports extensibility by enabling users to create new tags.

• Semantic information. An HTML-based search engine cannot distinguish between a document authored by "John Brightly" or a document that describes a star that shines "brightly." On the other hand, XML builds semantic information into documents, making it possible to know the meaning of a document.

Besides these benefits, XML is an easily readable, tree-based, and easy-to-write language.

In order to view an XML document, it must be interpreted. An XML parser is used to interpret an XML file. The parser loads the XML file, validates the XML document, and creates a document tree structure or a data structure. Some browsers, such as Internet Explorer 5, have a built-in XML parser.

Some of the common specifications related to XML include:

• DTD (Document Type Definition). DTDs specify the rules for XML documents that make it easier for everyone to understand the structure and logic of your XML documents.

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  DOM (Document Object Model). DOM enables navigation and modification in an XML document including adding, updating, or deleting content of elements. This also allows you to access XML data program- matically.

• XML schemas. XML schemas can be considered as a superset of DTDs and are also used to define the structure of XML documents.